The decision to ground the Short-Range Attack Missile-A, or SRAM-A, was based on concerns that an accident could result in plutonium dust, a potent cancer causing agent, being spread over a large area.Cheney issued a temporary order June 8 barring the missile from being loaded on B-52, B-1 and FB-111 bombers after the directors of three nuclear weapons laboratories expressed fears over the "remote" possibility of such an accident in testimony to Congress.

His decision to make the ban permanent follows an internal Air Force and Energy Department assessment that substantiated the scientists' concerns, according to Air Force Lt. Col. Rick Oborn.

The order does not prohibit other nuclear weapons, including longer-range missiles and gravity bombs, from being loaded aboard any of the nation's 372 strategic bombers while they are on "ground alert" status.